The present invention relates generally to an apparatus and method for controlling elevator car doors and, in particular, to an apparatus and method for controlling elevator doors with a continuous travel curve.
A door drive having a motor connected to a door mechanism by a shaft is shown in the U.S. Pat. No. 4,980,618. A current supply controlled by a microcomputer feeds electrical power to the motor. The rotational direction and rotational speed of the shaft are detected by a sensor and input to the microcomputer which controls the opening, closing and, in the case of obstacles, reversing of the door according to a predetermined speed profile. During the operations of opening and closing, the door is accelerated from a minimum speed to a maximum speed, maintained at the maximum speed and retarded to the minimum speed shortly before the end of the opening or closing operation. If the door meets an obstacle during the operations of openings and closing, the door is reversed according to two procedures implemented in the microcomputer. In a first procedure, the reversing operation is initiated on the basis of a speed change. A drop in the speed of the door below a certain speed value indicates to the microcomputer that an obstacle has been encountered in the travel path of the door, which indication initiates the reversing operation. In a second procedure, the reversing operation is initiated by sudden reversal of the travel direction of the door.
A disadvantage of the above described apparatus is that no optimization of the movement of the door is possible since the predetermined speed profile consists of straight line segments.